Question: How many animals have you studied in how many different enviroments?

Edward Codling answered on 15 Jun 2011:

Hi gyalzz

I think I answered a very similar question from you in another post so I’ll go into a bit more detail about some of the msot recent animal studies we have done:

1. Plankton
We have been trying to film different types and sizes of plankton as they swim around. Plankton are made up of thousands of tiny bug-like creatures that you can usually only see with a microscope (although some you can just see with the naked eye). We are interested in how the plankton interact – e.g. do big ones eat small ones and if so, how do they find them? To answer these questions we try to film them under different conditions and then analyse how individual plankton are swimming. This is quite tricky to do though as we have to use 2 cameras (to film in 3-d) and then also use a microscope at the same time.

2. Coral reef fish (copied from an earlier post!)
How does Nemo get home?
If you’ve watched Finding Nemo then you should recognise the stripy orange clownfish: http://en.wikipedia.org/wiki/Orange_clownfish

Clownfish eggs are laid on the coral reef but when they hatch the tiny baby clownfish (known as ‘larval’ fish) leave the reef and head out to the open ocean (the ‘pelagic’ environment). The reason they do this is because if they stay on the reef they’ll very quickly get eaten by bigger fish (which can include their own parents if they are unlucky!) The baby fish then live for a few weeks out in the open ocean eating plankton. Once they reach a certain size they then need to get back to a coral reef to ‘settle’ and become adult fish. This settlement involves a process known as ‘metamorphosis’ where the fish actually physically change (e.g. they go from see-through to having colour) – this is a bit like when tadpoles change into adult frogs. Unfortunately for the baby fish there is a very short time limit for them to do this – if they don’t find the reef in time then they’ll die!

The key problem we are interested in is how do the baby larval fish find a coral reef to get back to when they need to settle? Clearly they are only very small and people used to think it was just random whether they would return to a reef (e.g. if they were lucky enough to find a favourable current in the sea). However, recent work by my colleague Steve Simpson (and a few other people) have shown that the larval fish actually seem to respond to the sound of the coral reef (which is actually very noisy – fish ‘talk’ to each other all the time using croaks and ‘burps’!).

We have done some theoretical simulation work showing how important it is that they respond to sound and navigate towards it – this can greatly increase their chances of surviving. One of the things we are now interested in is whether the baby larval fish navigate to the coral reef as a group or as individuals – if we can determine this then it could have big implications about how we should manage and maintain coral reef ecosystems. We have a PhD student studying this problem at the moment – he has set up an experimental arena using a child’s paddling pool (!) and we are currently doing simple experiments to see how the fish behave under different conditions. In fact the student is about to go off to Indonesia for 2 months to study fish in their natural environment on the coral reef (while I have to stay at home unfortunately!).